Among fixing members for vehicles are, for example, brackets for holding registers for air conditioners, clusters, and the like, and the brackets are disposed on the back side of the instrument panels of automobiles. In recent years, a molded article made of a foamed resin, i.e. a foamed resin molded article is used for such a bracket from the viewpoint of reduction of the weight. Foamed resin molded articles are typically molded by a material, to be molded, which contains a resin material, such as polypropylene, polyethylene, or the like, and a foaming agent, being injected and filled into a cavity of a mold having a movable mold portion, and the movable mold portion being thereafter moved back by core-back. The foamed resin molded article thus molded has a porous foamed layer in which foam is formed by the foaming agent. In other words, the foamed resin molded article has a relatively low density thereinside, and therefore, is lightweight as compared to solid resin molded articles having no foamed layers.
A foamed resin molded article such as a bracket for use in an automobile has a mounting hole for fixing the article itself to a counterpart member or for positioning the article itself, or the like. For example, a screw, a clip mounted on a clip seat, or the like, is inserted into the mounting hole.
It is known that, in a foamed resin molded article formed by core-back molding, so-called “shape sag” having a round portion may occur at edge sections thereof or an opening peripheral edge section of the mounting hole. When such shape sag occurs at the opening peripheral edge section of the mounting hole, the dimensional precision of the mounting hole decreases, and therefore, the opening peripheral edge section may not assuredly have a desired thickness. If the opening peripheral edge section does not have a sufficient thickness, a clip or the like may not be stably fixed. Also, since shape sag occurring at the opening peripheral edge section of the mounting hole causes decrease of the thickness, the opening peripheral edge section may not assuredly have a sufficient load resistance. In such a case, the foamed resin molded article is not sufficiently fixed to a counterpart member, and therefore, unusual sound is likely to occur due to the loose attachment.
Under these circumstances, a molding technique for inhibiting the occurrence of shape sag as described above is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2007-130966 (hereinafter, referred to as Patent Literature 1). In the molding technique disclosed in Patent Literature 1, a protrusion for forming a mounting hole is provided in a movable mold portion, and a finely uneven portion is provided on the outer peripheral surface of the protrusion. During the core-back process, the movable mold portion is moved back while the finely uneven portion engages with and holds a material, to be molded, which is in contact with the outer peripheral surface of the protrusion. Therefore, the material to be molded is allowed to follow the mold surface of the movable mold portion during the core-back process. In other words, the opening peripheral edge section of the mounting hole is molded so as to have a shape along the mold surface of the movable mold portion. Thus, according to the molding technique disclosed in Patent Literature 1, the occurrence of shape sag is inhibited at the opening peripheral edge section of the mounting hole.
However, in the molding technique disclosed in Patent Literature 1, the foamed layer in which foam is formed by the foaming agent is also formed by core-back molding in the opening peripheral edge section of the mounting hole. As described above, the foamed layer is porous, that is, has a relatively low density, and therefore, has a low load resistance. Therefore, there is still a problem that the opening peripheral edge section of the mounting hole has a reduced load resistance.